Herbicide-resistant sunflower plants and methods of use

ABSTRACT

Novel herbicide-resistant sunflower plants designated as MUT31 and herbicide-resistant descendents thereof are provided. The MUT31 sunflower plants and the herbicide-resistant descendents thereof comprise increased resistance to at least one imidazolinone herbicide, when compared to wild-type sunflower plants. Methods for controlling weeds in the vicinity of these herbicide-resistant sunflower plants and methods for increasing the herbicide-resistance of a sunflower plant are also provided.

FIELD OF THE INVENTION

This invention relates to the field of agricultural biotechnology,particularly to herbicide-resistant sunflower plants and novelpolynucleotide sequences that encode wild-type and herbicide-resistantsunflower acetohydroxyacid synthase large subunit proteins.

BACKGROUND OF THE INVENTION

Acetohydroxyacid synthase (AHAS; EC 4.1.3.18, also known as acetolactatesynthase or ALS), is the first enzyme that catalyzes the biochemicalsynthesis of the branched chain amino acids valine, leucine andisoleucine (Singh (1999) “Biosynthesis of valine, leucine andisoleucine,” in Plant Amino Acid, Singh, B. K., ed., Marcel Dekker Inc.New York, N.Y., pp. 227-247). AHAS is the site of action of fivestructurally diverse herbicide families including the sulfonylureas(LaRossa and Falco (1984) Trends Biotechnol. 2:158-161), theimidazolinones (Shaner et al. (1984) Plant Physiol. 76:545-546), thetriazolopyrimidines (Subramanian and Gerwick (1989) “Inhibition ofacetolactate synthase by triazolopyrimidines,” in Biocatalysis inAgricultural Biotechnology, Whitaker, J. R. and Sonnet, P. E. eds., ACSSymposium Series, American Chemical Society, Washington, D.C., pp.277-288), and the pyrimidyloxybenzoates (Subramanian et al. (1990) PlantPhysiol. 94: 239-244). Imidazolinone and sulfonylurea herbicides arewidely used in modern agriculture due to their effectiveness at very lowapplication rates and relative non-toxicity in animals. By inhibitingAHAS activity, these families of herbicides prevent further growth anddevelopment of susceptible plants including many weed species. Severalexamples of commercially available imidazolinone herbicides are PURSUIT®(imazethapyr), SCEPTER® (imazaquin) and ARSENAL® (imazapyr). Examples ofsulfonylurea herbicides are chlorsulfuron, metsulfuron methyl,sulfometuron methyl, chlorimuron ethyl, thifensulfuron methyl,tribenuron methyl, bensulfuron methyl, nicosulfuron, ethametsulfuronmethyl, rimsulfuron, triflusulfuron methyl, triasulfuron, primisulfuronmethyl, cinosulfuron, amidosulfuron, flazasulfuron, imazosulfuron,pyrazosulfuron ethyl and halosulfuron.

Due to their high effectiveness and low-toxicity, imidazolinoneherbicides are favored for application by spraying over the top of awide area of vegetation. The ability to spray a herbicide over the topof a wide range of vegetation decreases the costs associated with plantestablishment and maintenance, and decreases the need for sitepreparation prior to use of such chemicals. Spraying over the top of adesired tolerant species also results in the ability to achieve maximumyield potential of the desired species due to the absence of competitivespecies. However, the ability to use such spray-over techniques isdependent upon the presence of imidazolinone-resistant species of thedesired vegetation in the spray over area.

Among the major agricultural crops, some leguminous species such assoybean are naturally resistant to imidazolinone herbicides due to theirability to rapidly metabolize the herbicide compounds (Shaner andRobinson (1985) Weed Sci. 33:469-471). Other crops such as corn(Newhouse et al. (1992) Plant Physiol. 100:882-886) and rice (Barrett etal. (1989) Crop Safeners for Herbicides, Academic Press, New York, pp.195-220) are somewhat susceptible to imidazolinone herbicides. Thedifferential sensitivity to the imidazolinone herbicides is dependent onthe chemical nature of the particular herbicide and differentialmetabolism of the compound from a toxic to a non-toxic form in eachplant (Shaner et al. (1984) Plant Physiol. 76:545-546; Brown et al.,(1987) Pestic. Biochem. Physiol. 27:24-29). Other Plant Physiologicaldifferences such as absorption and translocation also play an importantrole in sensitivity (Shaner and Robinson (1985) Weed Sci. 33:469-471).

Plants resistant to imidazolinones, sulfonylureas, triazolopyrimidines,and pyrimidyloxybenzoates have been successfully produced using seed,microspore, pollen, and callus mutagenesis in Zea mays, Arabidopsisthaliana, Brassica napus (i.e., canola) Glycine max, Nicotiana tabacum,sugarbeet (Beta vulgaris) and Oryza sativa (Sebastian et al. (1989) CropSci. 29:1403-1408; Swanson et al., 1989 Theor. Appl. Genet. 78:525-530;Newhouse et al. (1991) Theor. Appl. Genet. 83:65-70; Sathasivan et al.(1991) Plant Physiol. 97:1044-1050; Mourand et al. (1993) J. Heredity84:91-96; Wright and Penner (1998) Theor. Appl. Genet. 96:612-620; U.S.Pat. No. 5,545,822). In all cases, a single, partially dominant nucleargene conferred resistance. Four imidazolinone-resistant wheat plantswere also previously isolated following seed mutagenesis of Triticumaestivum L. cv. Fidel (Newhouse et al. (1992) Plant Physiol.100:882-886). Inheritance studies confirmed that a single, partiallydominant gene conferred resistance. Based on allelic studies, theauthors concluded that the mutations in the four identified lines werelocated at the same locus. One of the Fidel cultivar resistance geneswas designated FS-4 (Newhouse et al. (1992) Plant Physiol. 100:882-886).

Naturally occurring plant populations that were discovered to beresistant to imidazolinone and/or sulfonylurea herbicides have also beenused to develop herbicide-resistant sunflower breeding lines. Recently,two sunflower lines that are resistant to a sulfonylurea herbicide weredeveloped using germplasm originating from a wild population of commonsunflower (Helianthus annuus) as the source of the herbicide-resistancetrait (Miller and Al-Khatib (2004) Crop Sci. 44:1037-1038). Previously,White et al. ((2002) Weed Sci. 50:432-437) had reported that individualsfrom a wild population of common sunflower from South Dakota, U.S.A.were cross-resistant to an imidazolinone and a sulfonylurea herbicide.Analysis of a portion of the coding region of the acetohydroxyacidsynthase large subunit (AHASL) genes of individuals from this populationrevealed a point mutation that results in an Ala-to-Val amino acidsubstitution in the sunflower AHASL protein that corresponds to Ala205in the wild-type Arabidopsis thaliana AHASL protein (White et al. (2003)Weed Sci. 51:845-853).

Computer-based modeling of the three dimensional conformation of theAHAS-inhibitor complex predicts several amino acids in the proposedinhibitor binding pocket as sites where induced mutations would likelyconfer selective resistance to imidazolinones (Ott et al. (1996) J. Mol.Biol. 263:359-368). Wheat plants produced with some of these rationallydesigned mutations in the proposed binding sites of the AHAS enzyme havein fact exhibited specific resistance to a single class of herbicides(Ott et al. (1996) J. Mol. Biol. 263:359-368).

Plant resistance to imidazolinone herbicides has also been reported in anumber of patents. U.S. Pat. Nos. 4,761,373, 5,331,107, 5,304,732,6,211,438, 6,211,439 and 6,222,100 generally describe the use of analtered AHAS gene to elicit herbicide resistance in plants, andspecifically discloses certain imidazolinone-resistant corn lines. U.S.Pat. No. 5,013,659 discloses plants exhibiting herbicide resistance dueto mutations in at least one amino acid in one or more conservedregions. The mutations described therein encode either cross-resistancefor imidazolinones and sulfonylureas or sulfonylurea-specificresistance, but imidazolinone-specific resistance is not described. U.S.Pat. No. 5,731,180 and U.S. Pat. No. 5,767,361 discuss an isolated genehaving a single amino acid substitution in a wild-type monocot AHASamino acid sequence that results in imidazolinone-specific resistance.In addition, rice plants that are resistant to herbicides that interferewith AHAS have been developed by mutation breeding and also by theselection of herbicide-resistant plants from a pool of rice plantsproduced by anther culture. See, U.S. Pat. Nos. 5,545,822, 5,736,629,5,773,703, 5,773,704, 5,952,553 and 6,274,796.

In plants, as in all other organisms examined, the AHAS enzyme iscomprised of two subunits: a large subunit (catalytic role) and a smallsubunit (regulatory role) (Duggleby and Pang (2000) J. Biochem. Mol.Biol. 33:1-36). The AHAS large subunit (also referred to herein asAHASL) may be encoded by a single gene as in the case of Arabidopsis,rice, and sugar beet or by multiple gene family members as in maize,canola, and cotton. Specific, single-nucleotide substitutions in thelarge subunit confer upon the enzyme a degree of insensitivity to one ormore classes of herbicides (Chang and Duggleby (1998) Biochem J.333:765-777).

For example, bread wheat, Triticum aestivum L., contains threehomologous acetohydroxyacid synthase large subunit genes. Each of thegenes exhibit significant expression based on herbicide response andbiochemical data from mutants in each of the three genes (Ascenzi et al.(2003) International Society of Plant Molecular Biologists Congress,Barcelona, Spain, Ref. No. 510-17). The coding sequences of all threegenes share extensive homology at the nucleotide level (WO 03/014357).Through sequencing the AHASL genes from several varieties of Triticumaestivum, the molecular basis of herbicide tolerance in mostIMI-tolerant (imidazolinone-tolerant) lines was found to be the mutation5653(At)N, indicating a serine to asparagine substitution at a positionequivalent to the serine at amino acid 653 in Arabidopsis thaliana (WO03/01436; WO 03/014357). This mutation is due to a single nucleotidepolymorphism (SNP) in the DNA sequence encoding the AHASL protein.

Multiple AHASL genes are also know to occur in dicotyledonous plantsspecies. Recently, Kolkman et al. ((2004) Theor. Appl. Genet. 109:1147-1159) reported the identification, cloning, and sequencing forthree AHASL genes (AHASL1, AHASL2, and AHASL3) from herbicide-resistantand wild type genotypes of sunflower (Helianthus annuus L.). Kolkman etal. reported that the herbicide-resistance was due either to thePro197Leu (using the Arabidopsis AHASL amino acid position nomenclature)substitution or the Ala205Val substitution in the AHASL1 protein andthat each of these substitutions provided resistance to bothimidazolinone and sulfonylurea herbicides.

Given their high effectiveness and low-toxicity, imidazolinoneherbicides are favored for agricultural use. However, the ability to useimidazolinone herbicides in a particular crop production system dependsupon the availability of imidazolinone-resistant varieties of the cropplant of interest. To produce such imidazolinone-resistant varieties,plant breeders need to develop breeding lines with theimidazolinone-resistance trait. Thus, additional imidazolinone-resistantbreeding lines and varieties of crop plants, as well as methods andcompositions for the production and use of imidazolinone-resistantbreeding lines and varieties, are needed.

SUMMARY OF THE INVENTION

The present invention provides sunflower plants having increasedresistance to at least one herbicide when compared to a wild-typesunflower plant. In particular, the sunflower plants of the inventionhave increased resistance to at least one imidazolinone herbicide,particularly imazamox and/or imazapyr, when compared to a wild-typesunflower plant. Unlike previously described imidazolinone-resistantsunflower plants, the sunflower plants of the present invention comprisea novel herbicide-resistance mechanism that does not involve a mutationin gene encoding an acetohydroxyacid synthase large subunit (AHASL)protein. The sunflower plants of the invention also include seeds andprogeny plants that comprise at least one copy of a gene orpolynucleotide encoding a herbicide-resistant AHASL protein of theinvention.

In one embodiment, the present invention provides herbicide-resistantsunflower plants that are from the sunflower line that has beendesignated herein as MUT31. A sample of seeds of the MUT31 line has beendeposited with the American Type Culture Collection (ATCC) as ATCCPatent Deposit No. PTA-7839. The present invention further providesseeds, progeny plants and other descendent plants that comprise theherbicide-resistance characteristics of MUT31.

The present invention provides methods for controlling weeds in thevicinity of the herbicide-resistant sunflower plants of the invention.The methods comprises applying an effective amount of an herbicide tothe weeds and to the herbicide-resistant sunflower plant, wherein theherbicide-resistant sunflower plant has increased resistance to at leastone herbicide, particularly an imidazolinone herbicide, moreparticularly imazamox, when compared to a wild-type sunflower plant. Theherbicide can be, for example, applied to the foliage of the plants, tothe seeds of the plants prior to planting, and/or to the soil before orafter planting.

The present invention further provides methods for producing aherbicide-resistant sunflower plant. The methods involve crossing afirst sunflower plant comprising resistance to a herbicide to a secondsunflower plant that is not resistant to the herbicide, wherein thefirst sunflower plant comprises the herbicide-resistance characteristicsof MUT31, particularly a MUT31 sunflower plant or anyherbicide-resistant descendent of MUT31. Such a herbicide resistantthereof comprises the herbicide-resistance characteristics of MUT31,representative seeds of MUT 31 having been deposited with the ATCC asPatent Deposit Number PTA-7839. The methods further involve selectingfor a progeny plant that is resistant to the herbicide.

Additionally, the present invention provides methods for increasing theherbicide-resistance of a sunflower plant. The methods involve crossinga first sunflower plant comprising resistance to a herbicide to a secondsunflower plant, wherein the first sunflower plant comprises theherbicide-resistance characteristics of MUT31, particularly a MUT31sunflower plant or any herbicide-resistant descendent of MUT31. Thesecond sunflower plant can, but is not required to, comprise resistanceto at least one herbicide. The methods further involve selecting for aprogeny plant that comprises increased herbicide resistance whencompared to the herbicide resistance of the second sunflower plant. Inone embodiment of the invention, the second sunflower plant comprises atleast one herbicide-resistant AHASL gene. Such a second sunflower plantcomprises enhanced resistance one or more AHAS-inhibiting herbicides,particularly an imidazolinone herbicide.

BRIEF DESCRIPTION THE DRAWINGS

FIG. 1 is a graphical representation of the results of a 2'3×2 factorialexperiment to the test the effects of sunflower genotype (RHA266 orMUT31), herbicide dose (0, 0.25×, and, 0.50×; where X=50 g a.i./haimazamox), and malathion (0 or 1000 g a.i./ha). The sunflower plantswere at the 3-4 leaf growth stage at time of malathion and herbicidespraying. Malathion was sprayed on the plants 30 minutes prior to theimazamox spraying. The sunflower plants were evaluated at 7 days afterherbicide spraying to determine damage scores. Additional details areprovided below in Example 3.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to sunflower plants having increasedresistance to at least one herbicide when compared to wild-typesunflower plants. Herbicide-resistant sunflower plants were produced asdescribed hereinbelow by exposing wild-type (with respect to herbicideresistance) sunflower plants to a mutagen, allowing the plants to matureand reproduce, and selecting progeny plants that displayed enhancedresistance to the imidazolinone herbicide, imazamox, when compared tothe resistance of a wild-type sunflower plant to the imidazolinoneherbicide. The invention provides the novel herbicide-resistantsunflower line that is designated herein as MUT31. While the presentinvention is not bound by any particular biological mechanism, theherbicide-resistant sunflower plants of invention comprise a novelherbicide-resistance mechanism that is independent of a mutation ormutations in one or more AHASL genes. Thus, the present inventionprovides a new source of imidazolinone resistance that finds use inmethods for controlling weeds and also methods for producingherbicide-resistant sunflower plants or increasing the herbicideresistance of sunflower plants that already comprise herbicideresistance including, but not limited to, imidazolinone-resistance.

For the present invention, the terms “herbicide-tolerant” and“herbicide-resistant” are used interchangeable and are intended to havean equivalent meaning and an equivalent scope. Similarly, the terms“herbicide-tolerance” and “herbicide-resistance” are usedinterchangeable and are intended to have an equivalent meaning and anequivalent scope. Likewise, the terms “imidazolinone-resistant” and“imidazolinone-resistance” are used interchangeable and are intended tobe of an equivalent meaning and an equivalent scope as the terms“imidazolinone-tolerant” and “imidazolinone-tolerance”, respectively.

The present invention involves herbicide-tolerant or herbicide-resistantplants and methods for making and using such plants. A“herbicide-tolerant” or a “herbicide-resistant” plant is a plant that istolerant or resistant to at least one herbicide at a level that wouldnormally kill, or inhibit the growth of, a normal or wild-type plant.

In one embodiment of the invention, the methods of the present inventionfor increasing the herbicide resistance of a plant involve the use ofsunflower plants comprising herbicide-resistant AHASL polynucleotidesand herbicide-resistant AHASL proteins. A “herbicide-resistant AHASLpolynucleotide” is a polynucleotide that encodes a herbicide-resistantAHASL protein, wherein the protein comprises herbicide-resistant AHASactivity. A “herbicide-resistant AHASL protein” is an AHASL protein thatdisplays higher AHAS activity, relative to the AHAS activity of awild-type AHASL protein, when in the presence of at least one herbicidethat is known to interfere with AHAS activity and at a concentration orlevel of the herbicide that is to known to inhibit the AHAS activity ofthe wild-type AHASL protein. Furthermore, the AHAS activity of such aherbicide-tolerant or herbicide-resistant AHASL protein may be referredto herein as “herbicide-tolerant” or “herbicide-resistant” AHASactivity.

Furthermore, it is recognized that a herbicide-tolerant orherbicide-resistant AHASL protein can be introduced into a plant bytransforming a plant or ancestor thereof with a nucleotide sequenceencoding a herbicide-tolerant or herbicide-resistant AHASL protein. Suchherbicide-tolerant or herbicide-resistant AHASL proteins are encoded bythe herbicide-tolerant or herbicide-resistant AHASL polynucleotides.Alternatively, a herbicide-tolerant or herbicide-resistant AHASL proteinmay occur in a plant as a result of a naturally occurring or inducedmutation in an endogenous AHASL gene in the genome of a plant orprogenitor thereof. Nucleotide sequences encoding herbicide-resistantAHASL proteins and herbicide-resistant plants comprising an endogenousgene that encodes a herbicide-resistant AHASL protein are known in theart. See, for example, U.S. Pat. Nos. 5,013,659, 5,731,180, 5,767,361,5,545,822, 5,736,629, 5,773,703, 5,773,704, 5,952,553 and 6,274,796; allof which are herein incorporated by reference.

The present invention provides plants, plant tissues, and plant cellswith increased resistance or tolerance to at least one herbicide,particularly an imidazolinone herbicide, more particularly imazamox,imazapyr, or both imazamox and imazapyr. The preferred amount orconcentration of the herbicide is an “effective amount” or “effectiveconcentration.” By “effective amount” and “effective concentration” isintended an amount and concentration, respectively, that is sufficientto kill or inhibit the growth of a similar, wild-type, plant, planttissue, or plant cell, but that said amount does not kill or inhibit asseverely the growth of the herbicide-resistant plants, plant tissues,and plant cells of the present invention. Typically, the effectiveamount of a herbicide is an amount that is routinely used inagricultural production systems to kill weeds of interest. Such anamount is known to those of ordinary skill in the art, or can be easilydetermined using methods known in the art.

The methods of the present invention find use in increasing theherbicide resistance of a sunflower plant, including a sunflower plantthat comprises resistance to one or more herbicides, such as, forexample, those herbicides that inhibit or otherwise interfere or withthe activity of the wild-type AHAS enzyme. Such herbicides may also bereferred to herein as “AHAS-inhibiting herbicides” or simply “AHASinhibitors.” As used herein, an “AHAS-inhibiting herbicide” or an “AHASinhibitor” is not meant to be limited to single herbicide thatinterferes with the activity of the AHAS enzyme. Thus, unless otherwisestated or evident from the context, an “AHAS-inhibiting herbicide” or an“AHAS inhibitor” can be one herbicide or a mixture of two, three, four,or more herbicides, each of which interferes with the activity of theAHAS enzyme.

By “wild-type, sunflower plant, plant tissue, or plant cell” is intendeda sunflower plant, plant tissue, or plant cell, respectively, that lacksthe herbicide-resistance characteristics of the herbicide-resistantsunflower plants of the present invention, particularly MUT31 andherbicide-resistant descendents thereof. The use of the term “wild-type”is not, therefore, intended to imply that a sunflower plant, planttissue, or plant cell lacks recombinant DNA in its genome, and/or lacksherbicide-resistant characteristics that are different from thosedisclosed herein.

As used herein unless clearly indicated otherwise, the term “plant”intended to mean a plant at any developmental stage, as well as any partor parts of a plant that may be attached to or separate from a wholeintact plant. Such parts of a plant include, but are not limited to,organs, tissues, and cells of a plant. Examples of particular plantparts include a stem, a leaf, a root, an inflorescence, a flower, afloret, a fruit, a pedicle, a peduncle, a stamen, an anther, pollen, astigma, a style, an ovary, a petal, a sepal, a carpel, a root tip, aroot cap, a root hair, a leaf hair, a seed hair, a pollen grain, amicrospore, a cotyledon, a hypocotyl, an epicotyl, xylem, phloem,parenchyma, endosperm, a companion cell, a guard cell, and any otherknown organs, tissues, and cells of a plant. Furthermore, it isrecognized that a seed is a plant.

The sunflower plants of the present invention include bothnon-transgenic plants and transgenic plants. By “non-transgenic plant”is intended to mean a plant lacking recombinant DNA in its genome. By“transgenic plant” is intended to mean a plant comprising recombinantDNA in its genome. Such a transgenic plant can be produced byintroducing recombinant DNA into the genome of the plant. When suchrecombinant DNA is incorporated into the genome of the transgenic plant,progeny of the plant can also comprise the recombinant DNA. A progenyplant that comprises at least a portion of the recombinant DNA of atleast one progenitor transgenic plant is also a transgenic plant.

The present invention provides the herbicide-resistant sunflower linethat is referred to herein as MUT31. A deposit of at least 2500 seedsfrom sunflower (Helianthus annuus L.) line MUT31 was made under theBudapest Treaty with the Patent Depository of the American Type CultureCollection (ATCC), Manassas, Va. 20110 USA on Aug. 22, 2006 and assignedATCC Patent Deposit Number PTA-7839. The deposit of sunflower line MUT31was made for a term of at least 30 years and at least 5 years after themost recent request for the furnishing of a sample of the deposit isreceived by the ATCC. The deposit will be maintained under the terms ofthe Budapest Treaty on the International Recognition of the Deposit ofMicroorganisms for the Purposes of Patent Procedure. The deposit ofsunflower line MUT31 was made for a term of at least 30 years and atleast 5 years after the most recent request for the furnishing of asample of the deposit is received by the ATCC. Additionally, Applicantshave satisfied all the requirements of 37 C.F.R. §§1.801-1.809,including providing an indication of the viability of the sample.Applicants impose no restrictions on the availability of the depositedmaterial from the ATCC after the issuance of a patent from thisapplication. However, Applicants have no authority to wave anyrestrictions imposed by law on the transfer of biological material orits transportation in commerce. Applicants do not waive any infringementof Applicants' rights granted under such patent.

The present invention provides herbicide-resistant sunflower plants ofthe MUT31 line that were produced by a mutation breeding. Wild-typesunflower plants were mutagenized by exposing the plants to a mutagen,particularly a chemical mutagen, more particularly ethylmethanesulfonate (EMS). However, the present invention is not limited toherbicide-resistant sunflower plants that are produced by a mutagenesismethod involving the chemical mutagen EMS. Any mutagenesis method knownin the art may be used to produce the herbicide-resistant sunflowerplants of the present invention. Such mutagenesis methods can involve,for example, the use of any one or more of the following mutagens:radiation, such as X-rays, Gamma rays (e.g., cobalt 60 or cesium 137),neutrons, (e.g., product of nuclear fission by uranium 235 in an atomicreactor), Beta radiation (e.g., emitted from radioisotopes such asphosphorus 32 or carbon 14), and ultraviolet radiation (preferably from2500 to 2900 nm), and chemical mutagens such as base analogues (e.g.,5-bromo-uracil), related compounds (e.g., 8-ethoxy caffeine),antibiotics (e.g., streptonigrin), alkylating agents (e.g., sulfurmustards, nitrogen mustards, epoxides, ethylenamines, sulfates,sulfonates, sulfones, lactones), azide, hydroxylamine, nitrous acid, oracridines. Herbicide-resistant plants can also be produced by usingtissue culture methods to select for plant cells comprisingherbicide-resistance mutations and then regenerating herbicide-resistantplants therefrom. See, for example, U.S. Pat. Nos. 5,773,702 and5,859,348, both of which are herein incorporated in their entirety byreference.

Further details of mutation breeding can be found in “Principals ofCultivar Development” Fehr, 1993 Macmillan Publishing Company thedisclosure of which is incorporated herein by reference.

Sunflower plants and seeds of the present invention comprise theherbicide resistance characteristics of MUT31. Such plants and seeds maybe referred to herein as comprising the MUT31 trait. The MUT31 traitconfers resistance to imidazolinone herbicides to a plant or seedpossessing this trait whether the trait is in the heterozygous orhomozygous state in the plant. In particular, the MUT31 trait confers toa sunflower plant or seed resistance to at least one imidazolinoneherbicide, particularly imazamox and/or imazapyr, wherein theimidazolinone resistance is reduced or inhibited by the organophosphateinsecticide malathion. As described hereinbelow, the resistance ortolerance of MUT31 sunflower plants to the imidazolinone herbicideimazamox was found to be reduced or inhibited following the applicationof malathion to the MUT31 sunflower plants prior to the application ofimazamox. Thus, sunflower plants and seeds comprising the MUT31 traitcomprise malathion-inhibitable, imidazolinone resistance. While thepresent invention is not bound to a particular biological mechanism, theherbicide resistance of MUT31 sunflower plants or the MUT31 trait isbelieved to be due to an induced mutation in a single gene within thesunflower nuclear genome.

The sunflower plants of the present invention include, for example,descendents of the MUT31 line that are heterozygous or homozygous forthe MUT31 trait. It is recognized that such descendents can be producedvia sexual reproduction or by any asexual reproduction methods known inthe art such as for example, tissue culture. Descendents of the MUT31line that comprise the MUT31 trait can be identified by determining if adescendent sunflower plant comprises malathion-inhibitable,imidazolinone resistance. The present invention does not depend on aparticular method for determining if a descendent sunflower plantcomprises malathion-inhibitable, imidazolinone resistance. Any methodknown in the art can be used including the method disclosed in Example 3below to determine if a descendent of MUT31 comprisesmalathion-inhibitable, imidazolinone resistance. The method involvesapplying malathion to a descendent of MUT31 prior to the application ofthe imidazolinone herbicide and determining whether malathion reduces orinhibits the resistance of the descendent to the imidazolinoneherbicide. Descendents that comprise the MUT31 trait comprisemalathion-inhibitable, imidazolinone resistance. Thus, the sunflowerplants of the present invention include, for example, those sunflowerplants that are descendents of MUT31 and comprise malathion-inhibitable,imidazolinone resistance.

The present invention provides methods for enhancing the tolerance orresistance of a sunflower plant, plant tissue, plant cell, or other hostcell to at least one herbicide, particularly an imidazolinone herbicideor mixture two or more imidazolinone herbicides. For the presentinvention, the imidazolinone herbicides include, but are not limited to,PURSUIT® (imazethapyr), CADRE® (imazapic), RAPTOR® (imazamox), SCEPTER®(imazaquin), ASSERT® (imazethabenz), ARSENAL® (imazapyr), a derivativeof any of the aforementioned herbicides, and a mixture of two or more ofthe aforementioned herbicides, for example, imazapyr/imazamox(ODYSSEY®). More specifically, the imidazolinone herbicide can beselected from, but is not limited to,2-(4-isopropyl-4-methyl-5-oxo-2-imidiazolin-2-yl) -nicotinic acid,2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-3-quinolinecarboxylicacid, 5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-nicotinicacid,2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-(methoxymethyl)-nicotinicacid, 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-methylnicotinicacid, and a mixture of methyl6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluate and methyl2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate. The use of5-ethyl-2-(4-isopropyl-4-methyl-5-oxo- 2-imidazolin-2-yl) -nicotinicacid and2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-(methoxymethyl)-nicotinicacid is preferred. The use of2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-(methoxymethyl)-nicotinicacid is particularly preferred.

The herbicide-resistant plants of the invention find use in methods forcontrolling weeds. Thus, the present invention further provides a methodfor controlling weeds in the vicinity of a herbicide-resistant sunflowerplant of the invention. The method comprises applying an effectiveamount of a herbicide to the weeds and to the herbicide-resistantsunflower plant, wherein the plant has increased resistance to at leastone herbicide, particularly an imidazolinone or sulfonylurea herbicide,when compared to a wild-type plant. In such a method for controllingweeds, the herbicide-resistant plants of the invention are preferablycrop plants, including, but not limited to, sunflower, alfalfa, Brassicasp., soybean, cotton, safflower, peanut, tobacco, tomato, potato, wheat,rice, maize, sorghum, barley, rye, millet, and sorghum.

By providing plants having increased resistance to herbicides,particularly imidazolinone and sulfonylurea herbicides, a wide varietyof formulations can be employed for protecting plants from weeds, so asto enhance plant growth and reduce competition for nutrients. Aherbicide can be used by itself for pre-emergence, post-emergence,pre-planting and at planting control of weeds in areas surrounding theplants described herein or an imidazolinone herbicide formulation can beused that contains other additives. The herbicide can also be used as aseed treatment. That is an effective concentration or an effectiveamount of the herbicide, or a composition comprising an effectiveconcentration or an effective amount of the herbicide can be applieddirectly to the seeds prior to or during the sowing of the seeds.Additives found in an imidazolinone or sulfonylurea herbicideformulation or composition include other herbicides, detergents,adjuvants, spreading agents, sticking agents, stabilizing agents, or thelike. The herbicide formulation can be a wet or dry preparation and caninclude, but is not limited to, flowable powders, emulsifiableconcentrates and liquid concentrates. The herbicide and herbicideformulations can be applied in accordance with conventional methods, forexample, by spraying, irrigation, dusting, coating, and the like.

The present invention provides seeds with increased resistance to atleast one herbicide, particularly an imidazolinone herbicide. Such seedsinclude, for example, sunflower seeds that are herbicide-resistantdescendents of the MUT31 sunflower line.

A “descendent” of the MUT31 sunflower line comprises any plant, plantcell, or plant part that is derived by sexual and/or asexual propagationfrom MUT31, representative seeds of MUT31 having been deposited with theATCC and assigned ATCC Patent Deposit No. PTA-7839. For example, such adescendent includes a plant produced by crossing a first plant with asecond plant to produce a seed of the third plant (i.e., a descendent),wherein the first plant is a MUT31 sunflower plant and the second isanother sunflower plant that is not a MUT31 sunflower plant. Such adescendent also includes any plants that are descended from the thirdplant whether produced by sexual and/or asexual propagation. Forexample, cells, tissue or an organ from the third plant could be used toproduce a fourth plant by an asexual propagation method including, butnot limited to, in vitro plant cell, tissue, and organ culture methodsand methods involving the rooting of stem cuttings.

For the present invention, a herbicide-resistant descendent of MUT31 isa descendent of MUT31 that comprises the herbicide-resistancecharacteristics of MUT31 by way of being descended from one or moreMUT31 sunflower plants. In other words, such a herbicide-resistantdescendent has inherited the herbicide-resistance characteristics of aMUT31 sunflower plant by sexual reproduction, asexual reproduction, orcombination thereof.

Unless otherwise clearly indicated or apparent from the context, the“progeny” of a plant includes a plant of any subsequent generation whoseancestry can be traced to that plant. Similar, unless otherwise clearlyindicated by context, the “herbicide resistant progeny” of MUT31includes a plant of any subsequent generation whose ancestry can betraced to MUT31 and that comprises the herbicide-resistancecharacteristics of MUT31 by way of that ancestry.

The present invention provides methods for producing aherbicide-resistant sunflower plant, particularly a herbicide-resistantsunflower plant, through conventional plant breeding involving sexualreproduction. The methods comprise crossing a first plant comprisesresistance to a herbicide to a second plant that is not resistant to theherbicide. The first plant can be any of the herbicide-resistant plantsof the present invention including, for example, sunflower plants thatcomprise the herbicide-resistance characteristics of the MUT31 sunflowerplant, particularly MUT31 sunflower plants and herbicide-resistantdescendents of MUT31. The second plant can be any plant that is capableof producing viable progeny plants (i.e., seeds) when crossed with thefirst plant. Typically, but not necessarily, the first and second plantsare of the same species. The methods of the invention can furtherinvolve one or more generations of backcrossing the progeny plants ofthe first cross to a plant of the same line or genotype as either thefirst or second plant. Alternatively, the progeny of the first cross orany subsequent cross can be crossed to a third plant that is of adifferent line or genotype than either the first or second plant. Themethods of the invention can additionally involve selecting plants thatcomprise the herbicide-resistance characteristics of the first plant.

The present invention further provides methods for increasing theherbicide-resistance of a plant, particularly a herbicide-resistantsunflower plant, through conventional plant breeding involving sexualreproduction. The methods comprise crossing a first plant comprisesresistance to a herbicide to a second plant that may or may not beresistant to the herbicide or may be resistant to a different herbicideor herbicides than the first plant. The first plant can be any of theherbicide-resistant sunflower plants of the present invention including,for example, a MUT31 sunflower plants and a herbicide-resistantdescendent thereof. The second plant can be any plant that is capable ofproducing viable progeny plants (i.e., seeds) when crossed with thefirst plant. Typically, but not necessarily, the first and second plantsare of the same species. The progeny plants produced by this method ofthe present invention have increased or enhanced resistance to aherbicide when compared to either the first or second plant or both.When the first and second plants are resistant to different herbicides,the progeny plants will have the combined herbicide-resistancecharacteristics of the first and second plants. The methods of theinvention can further involve one or more generations of backcrossingthe progeny plants of the first cross to a plant of the same line orgenotype as either the first or second plant. Alternatively, the progenyof the first cross or any subsequent cross can be crossed to a thirdplant that is of a different line or genotype than either the first orsecond plant. The methods of the invention can additionally involveselecting plants that comprise the herbicide-resistance characteristicsof the first plant, the second plant, or both the first and the secondplant.

The present invention provides methods for enhancing or increasing theresistance of a sunflower plant to at least one imidazolinone herbicide.Imidazolinone herbicides are known as AHAS-inhibiting herbicides becauseof their recognized ability to inhibit AHAS activity in vivo and invitro. In addition to imidazolinone herbicides, AHAS-inhibitingherbicides include, for example, sulfonylurea herbicides,triazolopyrimidine herbicides, pyrimidinyloxybenzoate herbicides, andsulfonylamino-carbonyltriazolinone herbicides.

In an embodiment of the invention, the methods involve enhancing orincreasing the resistance of a herbicide-resistant sunflower plant thatcomprises resistance to an AHAS-inhibiting herbicide, wherein theresistance to the AHAS-inhibiting herbicide is due to one or moreherbicide-resistant AHASL proteins. Such a herbicide-resistant sunflowerplant can be resistant to one or more AHAS-inhibiting herbicides suchas, for example, an imidazolinone herbicide, a sulfonylurea herbicide, atriazolopyrimidine herbicide, a pyrimidinyloxybenzoate herbicide, asulfonylamino-carbonyltriazolinone herbicide, or mixture thereof.Examples of some suitable imidazolinone herbicides are described above.Sulfonylurea herbicides include, but are not limited to, chlorsulfuron,metsulfuron methyl, sulfometuron methyl, chlorimuron ethyl,thifensulfuron methyl, tribenuron methyl, bensulfuron methyl,nicosulfuron, ethametsulfuron methyl, rimsulfuron, triflusulfuronmethyl, triasulfuron, primisulfuron methyl, cinosulfuron, amidosulfuron,flazasulfuron, imazosulfuron, pyrazosulfuron ethyl, halosulfuron,azimsulfuron, cyclosulfuron, ethoxysulfuron, flazasulfuron,flupyrsulfuron methyl, foramsulfuron, iodosulfuron, oxasulfuron,mesosulfuron, prosulfuron, sulfosulfuron, trifloxysulfuron,tritosulfuron, a derivative of any of the aforementioned herbicides, anda mixture of two or more of the aforementioned herbicides. Thetriazolopyrimidine herbicides include, but are not limited to,cloransulam, diclosulam, florasulam, flumetsulam, metosulam, andpenoxsulam. The pyrimidinyloxybenzoate herbicides of the inventioninclude, but are not limited to, bispyribac, pyrithiobac, pyriminobac,pyribenzoxim and pyriftalid. The sulfonylamino-carbonyltriazolinoneherbicides include, but are not limited to, flucarbazone andpropoxycarbazone.

It is recognized that pyrimidinyloxybenzoate herbicides are closelyrelated to the pyrimidinylthiobenzoate herbicides and are generalizedunder the heading of the latter name by the Weed Science Society ofAmerica. Accordingly, the herbicides of the present invention furtherinclude pyrimidinylthiobenzoate herbicides, including, but not limitedto, the pyrimidinyloxybenzoate herbicides described above.

The sunflower plants of the present invention can be non-transgenic ortransgenic. Examples of non-transgenic sunflower plants having increasedresistance to at least one imidazolinone herbicide include the MUT31sunflower plant, representative seeds of MUT31 having been depositedwith the ATCC as Patent Deposit No. PTA-7839; or mutant, recombinant, ora genetically engineered derivative of MUT31; or of any progeny ofMUT31; or a plant that is a progeny of any of these plants; or a plantthat comprises the herbicide-resistance characteristics of MUT31,particularly a herbicide-resistant descendent of MUT31. An example of atransgenic sunflower plant having increased resistance to at least oneimidazolinone herbicide is a sunflower plant that is a geneticallyengineered derivative of MUT31 that comprises the herbicide-resistancecharacteristics of MUT31. Such a genetically engineered derivative cancomprises in its genome, for example, a transgene of interest including,but not limited to, a herbicide-resistant AHASL gene, a gene conferringdisease resistance, and a gene conferring insect resistance.

The present invention provides methods that involve the use of animidazolinone herbicide. In these methods, the imidazolinone herbicidecan be applied by any method known in the art including, but not limitedto, seed treatment, soil treatment, and foliar treatment.

Prior to application, the imidazolinone herbicide can be converted intothe customary formulations, for example solutions, emulsions,suspensions, dusts, powders, pastes and granules. The use form dependson the particular intended purpose; in each case, it should ensure afine and even distribution of the compound according to the invention.

The formulations are prepared in a known manner (see e.g., for reviewU.S. Pat. No. 3,060,084, EP-A 707 445 (for liquid concentrates),Browning, “Agglomeration”, Chemical Engineering, Dec. 4, 1967, 147-48,Perry's Chemical Engineer's Handbook, 4th Ed., McGraw-Hill, New York,1963, pages 8-57 and et seq. WO 91/13546, U.S. Pat. Nos. 4,172,714,4,144,050, 3,920,442, 5,180,587, 5,232,701, 5,208,030, GB 2,095,558,U.S. Pat. no. 3,299,566, Klingman, Weed Control as a Science, John Wileyand Sons, Inc., New York, 1961, Hance et al., Weed Control Handbook, 8thEd., Blackwell Scientific Publications, Oxford, 1989 and Mollet, H.,Grubemann, A., Formulation technology, Wiley VCH Verlag GmbH, Weinheim(Germany), 2001, 2. D. A. Knowles, Chemistry and Technology ofAgrochemical Formulations, Kluwer Academic Publishers, Dordrecht, 1998(ISBN 0-7514-0443-8), for example by extending the active compound withauxiliaries suitable for the formulation of agrochemicals, such assolvents and/or carriers, if desired emulsifiers, surfactants anddispersants, preservatives, antifoaming agents, anti-freezing agents,for seed treatment formulation also optionally colorants and/or bindersand/or gelling agents.

Examples of suitable solvents are water, aromatic solvents (for exampleSolvesso products, xylene), paraffins (for example mineral oilfractions), alcohols (for example methanol, butanol, pentanol, benzylalcohol), ketones (for example cyclohexanone, gamma-butyrolactone),pyrrolidones (NMP, NOP), acetates (glycol diacetate), glycols, fattyacid dimethylamides, fatty acids and fatty acid esters. In principle,solvent mixtures may also be used.

Examples of suitable carriers are ground natural minerals (for examplekaolins, clays, talc, chalk) and ground synthetic minerals (for examplehighly disperse silica, silicates).

Suitable emulsifiers are nonionic and anionic emulsifiers (for examplepolyoxyethylene fatty alcohol ethers, alkylsulfonates andarylsulfonates).

Examples of dispersants are lignin-sulfite waste liquors andmethylcellulose.

Suitable surfactants used are alkali metal, alkaline earth metal andammonium salts of lignosulfonic acid, naphthalenesulfonic acid,phenolsulfonic acid, dibutylnaphthalenesulfonic acid,alkylarylsulfonates, alkyl sulfates, alkylsulfonates, fatty alcoholsulfates, fatty acids and sulfated fatty alcohol glycol ethers,furthermore condensates of sulfonated naphthalene and naphthalenederivatives with formaldehyde, condensates of naphthalene or ofnaphthalenesulfonic acid with phenol and formaldehyde, polyoxyethyleneoctylphenol ether, ethoxylated isooctylphenol, octylphenol, nonylphenol,alkylphenol polyglycol ethers, tributylphenyl polyglycol ether,tristearylphenyl polyglycol ether, alkylaryl polyether alcohols, alcoholand fatty alcohol ethylene oxide condensates, ethoxylated castor oil,polyoxyethylene alkyl ethers, ethoxylated polyoxypropylene, laurylalcohol polyglycol ether acetal, sorbitol esters, lignosulfite wasteliquors and methylcellulose.

Substances which are suitable for the preparation of directly sprayablesolutions, emulsions, pastes or oil dispersions are mineral oilfractions of medium to high boiling point, such as kerosene or dieseloil, furthermore coal tar oils and oils of vegetable or animal origin,aliphatic, cyclic and aromatic hydrocarbons, for example toluene,xylene, paraffin, tetrahydronaphthalene, alkylated naphthalenes or theirderivatives, methanol, ethanol, propanol, butanol, cyclohexanol,cyclohexanone, isophorone, highly polar solvents, for example dimethylsulfoxide, N-methylpyrrolidone or water.

Also anti-freezing agents such as glycerin, ethylene glycol, propyleneglycol and bactericides such as can be added to the formulation.

Suitable antifoaming agents are for example antifoaming agents based onsilicon or magnesium stearate.

Suitable preservatives are for example Dichlorophen andenzylalkoholhemiformal.

Seed Treatment formulations may additionally comprise binders andoptionally colorants.

Binders can be added to improve the adhesion of the active materials onthe seeds after treatment. Suitable binders are block copolymers EO/POsurfactants but also polyvinylalcohols, polyvinylpyrrolidones,polyacrylates, polymethacrylates, polybutenes, polyisobutylenes,polystyrene, polyethyleneamines, polyethyleneamides, polyethyleneimines(Lupasol®, Polymin®), polyethers, polyurethanes, polyvinylacetate,tylose and copolymers derived from these polymers.

Optionally, also colorants can be included in the formulation. Suitablecolorants or dyes for seed treatment formulations are Rhodamin B, C.I.Pigment Red 112, C.I. Solvent Red 1, pigment blue 15:4, pigment blue15:3, pigment blue 15:2, pigment blue 15:1, pigment blue 80, pigmentyellow 1, pigment yellow 13, pigment red 112, pigment red 48:2, pigmentred 48:1, pigment red 57:1, pigment red 53:1, pigment orange 43, pigmentorange 34, pigment orange 5, pigment green 36, pigment green 7, pigmentwhite 6, pigment brown 25, basic violet 10, basic violet 49, acid red51, acid red 52, acid red 14, acid blue 9, acid yellow 23, basic red 10,basic red 108.

An examples of a suitable gelling agent is carrageen (Satiagel®).

Powders, materials for spreading, and dustable products can be preparedby mixing or concomitantly grinding the active substances with a solidcarrier.

Granules, for example coated granules, impregnated granules andhomogeneous granules, can be prepared by binding the active compounds tosolid carriers. Examples of solid carriers are mineral earths such assilica gels, silicates, talc, kaolin, attaclay, limestone, lime, chalk,bole, loess, clay, dolomite, diatomaceous earth, calcium sulfate,magnesium sulfate, magnesium oxide, ground synthetic materials,fertilizers, such as, for example, ammonium sulfate, ammonium phosphate,ammonium nitrate, ureas, and products of vegetable origin, such ascereal meal, tree bark meal, wood meal and nutshell meal, cellulosepowders and other solid carriers.

In general, the formulations comprise from 0.01 to 95% by weight,preferably from 0.1 to 90% by weight, of the imidazolinone herbicide. Inthis case, the imidazolinone herbicides are employed in a purity of from90% to 100% by weight, preferably 95% to 100% by weight (according toNMR spectrum). For seed treatment purposes, respective formulations canbe diluted 2-10 fold leading to concentrations in the ready to usepreparations of 0.01 to 60% by weight active compound by weight,preferably 0.1 to 40% by weight.

The imidazolinone herbicide can be used as such, in the form of theirformulations or the use forms prepared therefrom, for example in theform of directly sprayable solutions, powders, suspensions ordispersions, emulsions, oil dispersions, pastes, dustable products,materials for spreading, or granules, by means of spraying, atomizing,dusting, spreading or pouring. The use forms depend entirely on theintended purposes; they are intended to ensure in each case the finestpossible distribution of the imidazolinone herbicide according to theinvention.

Aqueous use forms can be prepared from emulsion concentrates, pastes orwettable powders (sprayable powders, oil dispersions) by adding water.To prepare emulsions, pastes or oil dispersions, the substances, as suchor dissolved in an oil or solvent, can be homogenized in water by meansof a wetter, tackifier, dispersant or emulsifier. However, it is alsopossible to prepare concentrates composed of active substance, wetter,tackifier, dispersant or emulsifier and, if appropriate, solvent or oil,and such concentrates are suitable for dilution with water.

The active compound concentrations in the ready-to-use preparations canbe varied within relatively wide ranges. In general, they are from0.0001 to 10%, preferably from 0.01 to 1% per weight.

The imidazolinone herbicide may also be used successfully in theultra-low-volume process (ULV), it being possible to apply formulationscomprising over 95% by weight of active compound, or even to apply theactive compound without additives.

The following are examples of formulations:

1. Products for dilution with water for foliar applications. For seedtreatment purposes, such products may be applied to the seed diluted orundiluted.

-   -   A) Water-soluble concentrates (SL, LS)    -    Ten parts by weight of the imidazolinone herbicide are        dissolved in 90 parts by weight of water or a water-soluble        solvent. As an alternative, wetters or other auxiliaries are        added. The imidazolinone herbicide dissolves upon dilution with        water, whereby a formulation with 10% (w/w) of imidazolinone        herbicide is obtained.    -   B) Dispersible concentrates (DC)    -    Twenty parts by weight of the imidazolinone herbicide are        dissolved in 70 parts by weight of cyclohexanone with addition        of 10 parts by weight of a dispersant, for example        polyvinylpyrrolidone. Dilution with water gives a dispersion,        whereby a formulation with 20% (w/w) of imidazolinone herbicide        is obtained.    -   C) Emulsifiable concentrates (EC)    -    Fifteen parts by weight of the imidazolinone herbicide are        dissolved in 7 parts by weight of xylene with addition of        calcium dodecylbenzenesulfonate and castor oil ethoxylate (in        each case 5 parts by weight). Dilution with water gives an        emulsion, whereby a formulation with 15% (w/w) of imidazolinone        herbicide is obtained.    -   D) Emulsions (EW, EO, ES)    -    Twenty-five parts by weight of the imidazolinone herbicide are        dissolved in 35 parts by weight of xylene with addition of        calcium dodecylbenzenesulfonate and castor oil ethoxylate (in        each case 5 parts by weight). This mixture is introduced into 30        parts by weight of water by means of an emulsifier machine        (e.g., Ultraturrax) and made into a homogeneous emulsion.        Dilution with water gives an emulsion, whereby a formulation        with 25% (w/w) of imidazolinone herbicide is obtained.    -   E) Suspensions (SC, OD, FS)    -    In an agitated ball mill, 20 parts by weight of the        imidazolinone herbicide are comminuted with addition of 10 parts        by weight of dispersants, wetters and 70 parts by weight of        water or of an organic solvent to give a fine imidazolinone        herbicide suspension. Dilution with water gives a stable        suspension of the imidazolinone herbicide, whereby a formulation        with 20% (w/w) of imidazolinone herbicide is obtained.    -   F) Water-dispersible granules and water-soluble granules (WG,        SG)    -    Fifty parts by weight of the imidazolinone herbicide are ground        finely with addition of 50 parts by weight of dispersants and        wetters and made as water-dispersible or water-soluble granules        by means of technical appliances (for example extrusion, spray        tower, fluidized bed). Dilution with water gives a stable        dispersion or solution of the imidazolinone herbicide, whereby a        formulation with 50% (w/w) of imidazolinone herbicide is        obtained.    -   G) Water-dispersible powders and water-soluble powders (WP, SP,        SS, WS)    -    Seventy-five parts by weight of the imidazolinone herbicide are        ground in a rotor-stator mill with addition of 25 parts by        weight of dispersants, wetters and silica gel. Dilution with        water gives a stable dispersion or solution of the imidazolinone        herbicide, whereby a formulation with 75% (w/w) of imidazolinone        herbicide is obtained.    -   I) Gel-Formulation (GF)    -    In an agitated ball mill, 20 parts by weight of the        imidazolinone herbicide are comminuted with addition of 10 parts        by weight of dispersants, 1 part by weight of a gelling agent        wetter and 70 parts by weight of water or of an organic solvent        to give a fine imidazolinone herbicide suspension. Dilution with        water gives a stable suspension of the imidazolinone herbicide,        whereby a formulation with 20% (w/w) of imidazolinone herbicide        is obtained. This gel formulation is suitable for us as a seed        treatment.

2. Products to be applied undiluted for foliar applications. For seedtreatment purposes, such products may be applied to the seed diluted.

-   -   A) Dustable powders (DP, DS)    -    Five parts by weight of the imidazolinone herbicide are ground        finely and mixed intimately with 95 parts by weight of finely        divided kaolin. This gives a dustable product having 5% (w/w) of        imidazolinone herbicide.    -   B) Granules (GR, FG, GG, MG)    -    One-half part by weight of the imidazolinone herbicide is        ground finely and associated with 95.5 parts by weight of        carriers, whereby a formulation with 0.5% (w/w) of imidazolinone        herbicide is obtained. Current methods are extrusion,        spray-drying or the fluidized bed. This gives granules to be        applied undiluted for foliar use.

Conventional seed treatment formulations include for example flowableconcentrates FS, solutions LS, powders for dry treatment DS, waterdispersible powders for slurry treatment WS, water-soluble powders SSand emulsion ES and EC and gel formulation GF. These formulations can beapplied to the seed diluted or undiluted. Application to the seeds iscarried out before sowing, either directly on the seeds.

In a preferred embodiment a FS formulation is used for seed treatment.Typically, a FS formulation may comprise 1-800 g/l of active ingredient,1-200 g/l Surfactant, 0 to 200 g/l antifreezing agent, 0 to 400 g/l ofbinder, 0 to 200 g/l of a pigment and up to 1 liter of a solvent,preferably water.

The present invention provides seeds of the herbicide-resistant plantsof the present invention, particularly seeds that areherbicide-resistant descendents of MUT31. For seed treatment, seeds ofthe present invention are treated with herbicides, preferably herbicidesselected from the group consisting of AHAS-inhibiting herbicides such asamidosulfuron, azimsulfuron, bensulfuron, chlorimuron, chlorsulfuron,cinosulfuron, cyclosulfamuron, ethametsulfuron, ethoxysulfuron,flazasulfuron, flupyrsulfuron, foramsulfuron, halosulfuron,imazosulfuron, iodosulfuron, mesosulfuron, metsulfuron, nicosulfuron,oxasulfuron, primisulfuron, prosulfuron, pyrazosulfuron, rimsulfuron,sulfometuron, sulfosulfuron, thifensulfuron, triasulfuron, tribenuron,trifloxysulfuron, triflusulfuron, tritosulfuron, imazamethabenz,imazamox, imazapic, imazapyr, imazaquin, imazethapyr, cloransulam,diclosulam, florasulam, flumetsulam, metosulam, penoxsulam, bispyribac,pyriminobac, propoxycarbazone, flucarbazone, pyribenzoxim, pyriftalid,pyrithiobac, and mixtures thereof, or with a formulation comprising aAHAS-inhibiting herbicide. Preferably, the AHAS-inhibiting herbicides ofthe present invention are imidazolinone herbicides.

The term seed treatment comprises all suitable seed treatment techniquesknown in the art, such as seed dressing, seed coating, seed dusting,seed soaking, and seed pelleting.

In accordance with one variant of the present invention, a furthersubject of the invention is a method of treating soil by theapplication, in particular into the seed drill: either of a granularformulation containing the imidazolinone herbicide as acomposition/formulation (e.g., a granular formulation, with optionallyone or more solid or liquid, agriculturally acceptable carriers and/oroptionally with one or more agriculturally acceptable surfactants. Thismethod is advantageously employed, for example, in seedbeds of cereals,maize, cotton, and sunflower.

The present invention also comprises seeds coated with or containingwith a seed treatment formulation comprising at least one ALS inhibitorselected from the group consisting of amidosulfuron, azimsulfuron,bensulfuron, chlorimuron, chlorsulfuron, cinosulfuron, cyclosulfamuron,ethametsulfuron, ethoxysulfuron, flazasulfuron, flupyrsulfuron,foramsulfuron, halosulfuron, imazosulfuron, iodosulfuron, mesosulfuron,metsulfuron, nicosulfuron, oxasulfuron, primisulfuron, prosulfuron,pyrazosulfuron, rimsulfuron, sulfometuron, sulfosulfuron,thifensulfuron, triasulfuron, tribenuron, trifloxysulfuron,triflusulfuron, tritosulfuron, imazamethabenz, imazamox, imazapic,imazapyr, imazaquin, imazethapyr, cloransulam, diclosulam, florasulam,flumetsulam, metosulam, penoxsulam, bispyribac, pyriminobac,propoxycarbazone, flucarbazone, pyribenzoxim, pyriftalid andpyrithiobac.

The term seed embraces seeds and plant propagules of all kinds includingbut not limited to true seeds, seed pieces, suckers, corms, bulbs,fruit, tubers, grains, cuttings, cut shoots and the like and means in apreferred embodiment true seeds.

The term “coated with and/or containing” generally signifies that theactive ingredient is for the most part on the surface of the propagationproduct at the time of application, although a greater or lesser part ofthe ingredient may penetrate into the propagation product, depending onthe method of application. When the said propagation product is(re)planted, it may absorb the active ingredient.

The seed treatment application with the imidazolinone herbicide or witha formulation comprising the imidazolinone herbicide is carried out byspraying or dusting the seeds before sowing of the plants and beforeemergence of the plants.

In the treatment of seeds, the corresponding formulations are applied bytreating the seeds with an effective amount of the imidazolinoneherbicide or a formulation comprising the imidazolinone herbicide.Herein, the application rates are generally from 0.1 g to 10 kg of thea.i. (or of the mixture of a.i. or of the formulation) per 100 kg ofseed, preferably from 1 g to 5 kg per 100 kg of seed, in particular from1 g to 2.5 kg per 100 kg of seed. For specific crops such as lettuce therate can be higher.

The present invention provides a method for combating undesiredvegetation or controlling weeds comprising contacting the seeds of theresistant plants according to the present invention before sowing and/orafter pregermination with an imidazolinone herbicide. The method canfurther comprise sowing the seeds, for example, in soil in a field or ina potting medium in greenhouse. The method finds particular use incombating undesired vegetation or controlling weeds in the immediatevicinity of the seed.

The control of undesired vegetation is understood as meaning the killingof weeds and/or otherwise retarding or inhibiting the normal growth ofthe weeds. Weeds, in the broadest sense, are understood as meaning allthose plants which grow in locations where they are undesired.

The weeds of the present invention include, for example, dicotyledonousand monocotyledonous weeds. Dicotyledonous weeds include, but are notlimited to, weeds of the genera: Sinapis, Lepidium, Galium, Stellaria,Matricaria, Anthemis, Galinsoga, Chenopodium, Urtica, Senecio,Amaranthus, Portulaca, Xanthium, Convolvulus, Ipomoea, Polygonum,Sesbania, Ambrosia, Cirsium, Carduus, Sonchus, Solanum, Rorippa, Rotala,Lindernia, Lamium, Veronica, Abutilon, Emex, Datura, Viola, Galeopsis,Papaver, Centaurea, Trifolium, Ranunculus, and Taraxacum.Monocotyledonous weeds include, but are not limited to, weeds of thegenera: Echinochloa, Setaria, Panicum, Digitaria, Phleum, Poa, Festuca,Eleusine, Brachiaria, Lolium, Bromus, Avena, Cyperus, Sorghum,Agropyron, Cynodon, Monochoria, Fimbristyslis, Sagittaria, Eleocharis,Scirpus, Paspalum, Ischaemum, Sphenoclea, Dactyloctenium, Agrostis,Alopecurus, and Apera.

In addition, the weeds of the present invention can include, forexample, crop plants that are growing in an undesired location. Forexample, a volunteer maize plant that is in a field that predominantlycomprises soybean plants can be considered a weed, if the maize plant isundesired in the field of soybean plants.

The articles “a” and “an” are used herein to refer to one or more thanone (i.e., to at least one) of the grammatical object of the article. Byway of example, “an element” means one or more elements.

As used herein, the word “comprising,” or variations such as “comprises”or “comprising,” will be understood to imply the inclusion of a statedelement, integer or step, or group of elements, integers or steps, butnot the exclusion of any other element, integer or step, or group ofelements, integers or steps. The following examples are offered by wayof illustration and not by way of limitation.

EXAMPLE 1 Mutagenesis of Helianthus annuus Line RHA266 and Selection ofImidazolinone-Resistant Plants

In the spring of the first growing season, forty rows of sunflower(Helianthus annuus) line RHA266 were sown outdoors at the AdvantaSemillas Biotech Research Station in Balcarce, BsAs, Argentina and thena portion of the plants were treated with ethyl methanesulfonate (EMS,also referred to as methanesulfonic acid ethyl ester). EMS is a knownmutagen that typically induces G·C-to-A·T transitions in DNA (Jander etal. (2003) Plant Physiol. 131:139-146). Plants were treated with asolution comprising 0.5%, 5%, or 10%, (w/v) EMS. For each EMS treatment,13 rows of sunflower plants were treated. Before flowering, all M₀plants were bagged in order to ensure that the resulting M₁ seeds werethe product of self-pollination. The seed heads from each EMS treatmentwere harvested and threshed in bulk. In the following growing season,the M₁ seeds were sown outdoors with each treatment in a separate plot.Twenty days later, when the plants were at the 2-4 leaf pair growthstage, all of the EMS-treated plants were sprayed with 2× of SWEEPER70DG (100 g a.i./ha). The active ingredient in SWEEPER is imazamox.After the herbicide spraying, a total of 54 plants survived and wereselected as putative resistant. Forty-four resistant plants reachedflowering, produced pollen, and M₂ seed. The distribution of theforty-four fertile resistant plants per EMS treatment is indicated inTable 1.

TABLE 1 Number of M1 Imidazolinone-Resistant Sunflower Plants Recoveredfrom Each EMS Treatment EMS Concentration (%) No. of Resistant PlantsRecovered 0.5 19 5.0 9 10 16

Tissue samples were taken from each individual surviving M1 plant andDNA from each sample was extracted for PCR amplification and sequencingstudies described below in Example 2.

M2 seeds that were produced by each of the forty-four fertile M1 plantswere sown in individual plots in Fargo, N.D. then sprayed with 0.5× ofSWEEPER 70DG (25 g ai/ha imazamox) at the 2-4 leaf pair growth stage.One of the plots was selected as homozygous tolerant and designated asMUT31. Nineteen M2 plants of MUT31 were harvested, their M2:3 progeniessown in Balcarce in the summer of 2003-2004, and the resulting plantsallowed to mature and then selfed. M4 seed from one plot was harvestedand declared breeder seed on the basis of phenotypic observations.(Breeder seed is seed produced by the direct control of the plantbreeder and is the basis of the first and recurring increase offoundation seeds.)

EXAMPLE 2 PCR Amplification and Sequencing of Sunflower PolynucleotidesEncoding Imidazolinone-Resistant and Wild-Type AHASL1 Proteins

To attempt to determine the origin of the imidazolinone tolerance in thesunflower plants of Example 1, polymerase chain reaction (PCR)amplification of genomic DNA was employed to amplify the entire codingregions of each to the sunflower AHASL 1, AHASL2, and AHASL3 genes. Forthe PCR amplifications, genomic DNA was isolated from tissue of the M₁MUT31 sunflower plant. Control, wild-type genomic DNA was also isolatedfrom tissue of an RHA266 sunflower plant for PCR amplifications of eachof the wild-type AHASL genes. The resulting PCR products were sequencedto determine the DNA sequences of the AHASL1, AHASL2, and AHASL3 genesfrom the MUT31 and RHA266 plants.

Surprisingly, when the DNA sequences of the AHASL1, AHASL2, and AHASL3genes from MUT31 were aligned and compared to their corresponding DNAsequences from RHA266, no differences were detected (data not shown).While the present invention is not bound by any particular biologicalmechanism, these results indicate that the sunflower plants of the MUT31comprise a novel herbicide-resistance mechanism that is independent of amutation or mutations in one or more AHASL genes.

EXAMPLE 3 Analysis of Herbicide Detoxification by MUT31

To evaluate the detoxification ability of MUT31 sunflower plants, anexperiment was conducted in the greenhouse. The objective of theexperiment was to determine if the imazamox tolerance of MUT31 plants isassociated with detoxification mechanism that is mediated by a P450monooxygenase enzyme (referred to herein as “P450 enzyme”). It waspreviously reported that the organophosphate insecticide malathion(diethyl-dimethoxythiophosphorylthio-succinate) specifically inhibitsP450 enzymes by blocking the herbicide detoxification activity (Yu etal. (2004) Pest. Biochem. Physiol. 78:21-30). Thus, plants comprisingenhanced herbicide tolerance that is due to an altered P450 enzyme areexpected to become less tolerant or susceptible to the herbicide whenmalthion is applied to the plants before they are treated with theherbicide.

A factorial experiment with three factors: genotypes (MUT31 and RHA266),herbicide dose (Control, 0.25×, and 0.50×; where X=50 g ai/ha imazamox)and malathion (with or without malathion) was arranged in a randomizedsplit-split plot block design. Imazamox (SWEEPER) was sprayed at the 3-4leaf growth stage. The P450 inhibitor malathion was sprayed at a rate of1000 g ai/ha 30 minutes prior to herbicide spraying. The evaluation ofthe plants was carried out seven days after herbicide spraying, usingthe criteria set forth in Table 2.

TABLE 2 Criteria for Herbicide Damage Scores for Plant EvaluationsSymptom Damage score Chlorosis, yellow flash  5-10% Growth ratereduction, internodes shortening 10-20% Leaf deformations 20-30%Necrosis 30-45% Dead plant +50%

The application of malathion in the absence of herbicide had no effecton the response of the MUT31 and RHA266 sunflower lines; both the meanand variance were zero (Table 3). Both lines were more tolerant (lowerdamage % score) when malathion was not sprayed before imazamox. When theplants were treated with 0.5× imazamox alone, MUT31 showed a significantincrease in herbicide tolerance with respect to the control RHA266. Theherbicide tolerance of MUT31 significantly decreased (higher score)after malathion treatment (Table 3, FIG. 1). The results of thestatistical analysis are presented in Table 4.

The results of this factorial experiment indicate that malathioninhibited the herbicide tolerance exhibited by MUT31 and suggest thatthe herbicide tolerant phenotype of MUT31 may be due to detoxificationmechanism mediated by one or more altered P450 enzymes. Although thepresent invention does not depend on any particular biological mechanismfor enhanced herbicide resistance, these results further suggest thatthe MUT31 sunflower plant comprises in its genome one or more mutationsin one or more genes encoding P450 enzymes.

TABLE 3 Mean Herbicide Damage Score Values Herbicide dose 0X (control)0.25X 0.50X Malathion No Yes No Yes No Yes MUT31 0.00 0.00 9.50 30.3520.13 40.31 RHA266 0.00 0.00 27.95 45.30 42.35 45.50

TABLE 4 Statistical Analysis of the Factorial Experiment MUT-31 andRHA266 Source Df MeanSq F Pr (>F) Significance Replicates 3 38.2Malathion 1 1893.43 122.01 0.001589 ** Error (a) 3 15.52 Herbicide dose1 619.08 34.966 0.001041 ** Malathion × dose 1 110.45 6.2381 0.046678 *Error (b) 6 17.71 Line 1 1849.08 101.6794 3.27E−07 *** Malathion × Line1 210.89 11.5969 0.005217 ** Dose × Line 1 17.93 0.9857 0.340397Malathion × Dose × 1 91.63 5.0388 0.044418 * Line Residuals 12 18.19

EXAMPLE 4 Herbicide Tolerance of Sunflower Lines with MUT31 and aHerbicide-Tolerant AHASL Gene

A field trial was conducted to compare the herbicide tolerance ofsunflower hybrids carrying the MUT31 trait and the A205V mutation in asunflower AHASL gene (A205V/A205V). A sunflower AHASL gene with theA205V mutation encodes a AHASL protein which has a valine at amino acidthat corresponds to amino acid position 205 in the Arabidopsis thalianaAHASL protein. The amino acid at the same position in a wild-typesunflower AHASL protein is alanine. In the amino acid sequence of thesunflower AHASL protein, this alanine-to-valine amino acid substitutionis at amino acid position 190. By convention, the sites of amino acidsubstitutions that are known to give rise to herbicide resistance inplant AHASL proteins are typically referred to by the position of thesubstitution in the amino acid sequence of the Arabidopsis AHASLprotein.

TABLE 5 Description of Sunflower Lines Tested Entry Entry Type ofMaterial Mut event Zygosity Description 1 IMI Restorer A205V homo hybrid2 IMI cms × IMI A205V homo hybrid restorer 3 WT × IMI restorer A205Vhetero hybrid 4 WT × IMI restorer A205V hetero hybrid 5 A837 cms × IMIA205V hetero hybrid restorer 6 IMI cms × MUT31 A205V/MUT31 hetero hybridrestorer 7 WT — — line 8 MUT31 Restorer MUT31 homo line

Seed from each entry was produced under optimum seed productionconditions in South America in 2005/2006. The field trial was conductedat one location in North Dakota, USA in 2006. The entries were organizedin a randomized complete block using a split plot design consisting of 3replications for each treatment combination. Factor A was the herbicidetreatment, and factor B was the sunflower entry. The plot size was 4rows×12 ft and the seeding rate was consistent with local agronomicpractices. The herbicide rates for each treatment for Entries 1-6 areshown in Table 6. The herbicide rates for each treatment for Entries 8are shown in Table 7. The spray volume was 10 gallons per acre (GPA) (or100 liters/ha) for a backpack sprayer or 20 GPA (or 200 liters/ha) for atractor mounted boom. The herbicide treatments were applied at the 2-4leaf growth stage.

TABLE 6 Factor A, Herbicide Treatment List for Entries 1-6: TreatmentNo. Treatment 1 Untreated 2 50 g ai/ha imazamox + 0.25% (v/v) NIS 3 100g ai/ha imazamox + 0.25% (v/v) NIS 4 200 g ai/ha imazamox + 0.25% (v/v)NIS 5 160 g ai/ha imazapyr + 0.25% (v/v) NIS NIS = non-ionic surfactant

TABLE 7 Factor A, Herbicide Treatment List for Entry 8: Treatment No.Treatment 1 Untreated 2 12.5 g ai/ha imazamox + 0.25% (v/v) NIS 3 25 gai/ha imazamox + 0.25% (v/v) NIS 4 37.5 g ai/ha imazamox + 0.25% (v/v)NIS 5 80 g ai/ha imazapyr + 0.25% (v/v) NIS NIS = non-ionic surfactant

Entry 7 (WT Maintainer line) was left unsprayed in all treatment blocks.Each herbicide treatment was tested on a WT border plot to ensureefficacy of the product (100% crop injury at 21 days post spray).

Phytotoxicity ratings were assessed at 7 days and 21 days followingherbicide application. Phytotoxicity was recorded as the amount of plantdamage (in percent), where a rating of ‘0’ indicated no damage to theplants in the plot relative to the untreated plot. A rating of ‘100’indicated complete necrosis (death) of the plants in the plot relativeto the untreated plot.

The data was subjected to an ANOVA analysis and the means from the 3repetitions are presented in Table 8 (phytotoxicity at 21 dayspost-treatment).

TABLE 8 Phytotoxicity Ratings (% Crop Injury) recorded 21 Days afterTreatment (DAT) 21 DAT 21 DAT 21 DAT 21 DAT Type of Mut 50 G 100 G 200 G160 G 21 DAT Entry Material event Zygosity IMAZAMOX IMAZAMOX IMAZAMOXIMAZAPYR UNTREATED 1 IMI Restorer A205 homo 5.00 6.67 15.00 6.67 0.00 2IMI cms x A205 homo 0.00 3.33 21.67 3.33 0.00 IMI restorer 3 WT x IMIA205 hetero 6.67 25.00 73.33 20.00 0.00 restorer 4 WT x IMI A205 hetero11.67 46.67 76.67 43.33 0.00 restorer 5 A837 cms x A205 hetero 3.3340.00 78.33 36.67 0.00 IMI restorer 6 IMI cms x A205/ hetero 1.67 10.0043.33 10.00 0.00 MUT31 MUT31 restorer 7 WT 0.00 0.00 0.00 0.00 0.00 21DAT 21 DAT 21 DAT 21 DAT Type of Mut 12.5 G 25 G 37.5 G 80 G 21 DATEntry Material event Zygosity IMAZAMOX IMAZAMOX IMAZAMOX IMAZAPYRUNTREATED 8 MUT31 MUT31 homo 15.00 25.00 46.67 88.33 0.00 Restorer LSD =8.89 CV = 56.78 St Dev = 5.55

The phytotoxicity in the heterozygous A205V entries (entries 3-5) wassignificantly higher than the double heterozygous A205V/MUT31 entry(entry 6) at 21 days after treatment with imazamox and imazapyr. Thehomozygous A205V entries (entries 1-2) demonstrated the lowest levels ofphytotoxicity or crop injury (Table 1). At 100 g ai/ha of imazamox therange in phytotoxicity of the A205V heterozygous entries was between 25%and 47% compared to an injury rating of 10% for the A205V/MUT31heterozygous entry. At 200 g ai/ha of imazamox the range inphytotoxicity of the A205V heterozygous entries was between 73% and 78%injury compared to an injury rating of 43% for the A205V/MUT31heterozygous entry. With 160 g ai/ha of imazapyr the range inphytotoxicity of the A205V heterozygous entries was between 20% and 43%injury compared to an injury rating of 10% for the A205V/MUT31heterozygous entry.

When MUT31 alone (entry 8) was challenged with 37.5 g ai/ha of imazamox,it demonstrated an injury rating of 47% at 21 days after treatment. Fromprevious studies (data not shown), MUT31 has demonstrated 100% cropinjury at rates of 75 g ai of imazamox per hectare and 100 g ai ofimazapyr per hectare.

The double heterozygous A205V/MUT31 entries demonstrated significantlyhigher herbicide tolerance to both imazamox and imazapyr treatmentsversus the heterozygous A205V/-entries and versus the MUT31 entry on itsown.

Based on this data, MUT31 when stacked with the A205V mutation in theheterozygous state provides stronger (enhanced) herbicide tolerance thanthe A205V mutation in the heterozygous state. Having a product thatworks in the heterozygous state at 2× x the commercial product rate (100g ai imazamox/ha and 160 g ai imazapyr/ha) is a great advantage tosunflower hybrid plant breeders over the current homozygous A205V/A205Vproduct, saving both time and resources in the breeding of imidazolinonetolerant sunflowers.

All publications and patent applications mentioned in the specificationare indicative of the level of those skilled in the art to which thisinvention pertains. All publications and patent applications are hereinincorporated by reference to the same extent as if each individualpublication or patent application was specifically and individuallyindicated to be incorporated by reference.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it will be obvious that certain changes and modificationsmay be practiced within the scope of the appended claims.

1-48. (canceled)
 49. A sunflower plant, or part thereof, comprisingboth: (a) the MUT31 trait of sunflower line MUT31, a representativesample of seed of said line having been deposited under ATCC PatentDeposit No. PTA-7839, wherein said MUT31 trait was produced by mutationbreeding and comprises imidazolinone herbicide tolerance, even in theabsence of an herbicide tolerant acetohydroxyacid synthase large subunit(AHASL) protein, and said herbicide tolerance is reducible orinhibitable by malathion; and (b) at least one herbicide tolerant AHASLgene wherein said sunflower plant exhibits greater AHAS-inhibitingherbicide tolerance than a sunflower plant containing, as the soleAHAS-inhibiting herbicide tolerance trait thereof, either said MUT31trait or said herbicide tolerant AHASL gene.
 50. The sunflower plant ofclaim 49, wherein the AHAS-inhibiting herbicide tolerance comprisesimidazolinone herbicide tolerance.
 51. The sunflower plant of claim 49,wherein said sunflower plant is selected from the group consisting of:(a) sunflower plants that are progeny of line MUT31; (b) sunflowerplants that are mutants, recombinants, or genetically engineeredderivatives of line MUT31; and (c) sunflower plants that are progeny ofat least one of the sunflower plants of (a)-(b).
 52. The sunflower plantof claim 49, wherein said at least one herbicide tolerant AHASL geneencodes an AHASL protein comprising an alanine-to valine amino acidsubstitution at amino acid position 190 or equivalent position relativeto the amino acid sequence of SEQ ID NO:2.
 53. The sunflower plant ofclaim 49, wherein said imidazolinone herbicide comprises at least oneof: 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-nicotinic acid,2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl) quinoline-3-carboxylicacid, 5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-nicotinicacid,2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-(methoxymethyl)-nicotinicacid, 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-methylnicotinicacid, a mixture of methyl6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluate and methyl2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate, or acombination of any of the foregoing.
 54. The sunflower plant of claim49, wherein said imidazolinone herbicide is imazamox, imazapyr,imazethapyr, or mixtures thereof.
 55. A seed of the sunflower plant ofclaim 49, wherein said seed is an imidazolinone-tolerant descendent of aplant of line MUT31 and comprises the imidazolinone herbicide tolerancetrait of line MUT31.
 56. The seed of claim 55, wherein said seed istreated with an imidazolinone herbicide.
 57. A cell of the plant ofclaim 49, wherein said cell comprises the imidazolinone herbicidetolerance trait of line MUT31
 58. A pollen grain of the plant of claim49, wherein said pollen grain comprises the imidazolinone herbicidetolerance trait of line MUT31.
 59. A method for controlling weeds in afield, said method comprising: growing in the field a sunflower plantcomprising both (a) the MUT31 trait of sunflower line MUT31, arepresentative sample of seed of said line having been deposited underATCC Patent Deposit No. PTA-7839, wherein said MUT31 trait was producedby mutation breeding and comprises imidazolinone herbicide tolerance,even in the absence of an herbicide tolerant acetohydroxyacid synthaselarge subunit (AHASL) protein, and said herbicide tolerance is reducibleor inhibitable by malathion; and (b) at least one herbicide tolerantAHASL gene wherein said sunflower plant exhibits greater AHAS-inhibitingherbicide tolerance than a sunflower plant containing, as the soleAHAS-inhibiting herbicide tolerance trait thereof, either said MUT31trait or said herbicide tolerant AHASL gene; and contacting saidsunflower plant and weeds in the field with an effective amount of animidazolinone herbicide to which the sunflower plant is tolerant andwhich would inhibit the growth of the wild-type variety of the sunflowerplant, thereby controlling the weeds.
 60. The method of claim 59,wherein the AHAS-inhibiting herbicide tolerance comprises imidazolinoneherbicide tolerance.
 61. The method of claim 59, wherein said sunflowerplant is selected from the group consisting of: (a) sunflower plantsthat are progeny of line MUT31; (b) sunflower plants that are mutants,recombinants, or genetically engineered derivatives of line MUT31; and(c) sunflower plants that are progeny of at least one of the sunflowerplants of (a)-(b).
 62. The method of claim 59, wherein saidimidazolinone herbicide comprises at least one of:2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-nicotinic acid,2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl) quinoline-3-carboxylicacid, 5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-nicotinicacid,2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-(methoxymethyl)-nicotinicacid, 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-methylnicotinicacid, a mixture of methyl6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluate and methyl2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate, or acombination of any of the foregoing.
 63. A method for combatingundesired vegetation comprising contacting a sunflower seed of asunflower plant of claim 49 before sowing and/or after pregerminationwith an imidazolinone herbicide.
 64. The method of claim 63, furthercomprising planting said sunflower seed in an environment favorable forgrowth of a sunflower plant.
 65. The methods of claim 64, wherein saidenvironment comprises undesired vegetation.
 66. A sunflower plant, orpart thereof, comprising the MUT31 trait of sunflower line MUT31, arepresentative sample of seed of said line having been deposited underATCC Patent Deposit No. PTA-7839, wherein said MUT31 trait was producedby mutation breeding and comprises imidazolinone herbicide tolerance,even in the absence of an herbicide tolerant acetohydroxyacid synthaselarge subunit (AHASL) protein, and said tolerance is reducible orinhibitable by malathion; and wherein said MUT31 trait being capable ofenhancing AHAS-inhibiting herbicide tolerance of a sunflower plantcomprising an herbicide tolerant AHASL gene, when the MUT31 trait isstacked with said herbicide tolerant AHASL gene in the plant.
 67. Thesunflower plant of claim 66, wherein the AHAS-inhibiting herbicidetolerance comprises imidazolinone herbicide tolerance.
 68. A method forenhancing the AHAS-inhibiting herbicide tolerance of a sunflower plant,comprising: providing in said sunflower plant both the MUT31 trait andan herbicide tolerant AHASL gene, wherein said sunflower plant exhibitsgreater AHAS-inhibiting herbicide tolerance than a sunflower plantcontaining, as the sole AHAS-inhibiting herbicide tolerance traitthereof, either said MUT31 trait or said herbicide tolerant AHASL gene.69. The method of claim 68, wherein the AHAS-inhibiting herbicidetolerance comprises imidazolinone herbicide tolerance.